In a medium sized bowl, sift or whisk the 1 1/2 cups all purpose flour with the 1/2 cup cornstarch and 1/4 teaspoon salt.
In the bowl of your electric stand mixer, fitted with the paddle attachment (or with a hand mixer), beat the 1 cup unsalted butter, at room temperature until smooth. Add the 1/4 cup confectioners sugar (powdered or icing) and beat until incorporated. Beat in the 1 1/2 teaspoons pure vanilla extract. Add the flour mixture and beat just until combined.
Cover and refrigerate the batter until firm (one to two hours).
Preheat your oven to 350 degrees F (180 degrees C). Line two baking sheets with parchment paper.
When batter is firm, roll into 1 inch (2.5 cm) balls, using about 1 tablespoon / 18 grams of batter. Place on the prepared baking sheet, spacing about 2 inches (5 cm) apart.
Bake for about 12–16 minutes or until the bottoms of the cookies are golden brown and the edges of the cookies are just starting to brown. Rotate your baking sheet front to back about halfway through baking.
Remove from oven and place on a wire rack to cool for 1–2 minutes.
Place 1 cup (120 grams) of sifted 1 cup confectioners sugar (powdered or icing), sifted on a plate and roll each cookie in the sugar. Transfer to a wire rack to cool completely and then roll the cookies again in the powdered sugar.
